People that learned with C (Pascal too) piss more straightforward code on average, and have better debugging skills. And they are more "aware" of the computer.
PS: I did go C, assembly (had to rewrite some libc functions) then emacs lisp (before trying to write stuff in Common Lisp). I don't think going assembly will help a webdev much (even if he work mostly on backend), but lisp is definitly helpfull for anyone. Assembly is great if you like having some fun, but beside CTF and "that one time" (i had a really nasty C bug), the stuff i learned while writing assembly were not really usefull to me.
What problems are you thinking of, specifically? In high school, I had a semester each of BASIC and C++, but my first serious programming was with Java in college. That is, beyond things like a "guess the number" game, getting into actual study of algorithms and data structures.
I'm mostly a C++ dev now, and I've never had complaints about my coding style. Then again, I never bought into the WidgetFactoryFactoryImpl kind of crap.
A language like C is already bad because there has to be a function before anything is done, instead of just a sequence of instructions to the machine to do something.
Imagine you told me "can you go to the cupboard and fetch the sugar?" and I said, "Nope: you must wrap that in an instruction sheet called "main", and then ask me to compile and execute it".